Signal control devices are used for a variety of applications, including control of the braking force applied to railway cars. Railway cars necessitate variations in braking power based on the weight of the contents in the railway car. If an inappropriate amount of braking force is applied to the railway car, the car may not stop or may shake along the track possibly leading to disengagement between the wheels and the track. In addition, when excessive brake force is applied, flat spots may form on the wheels that can result in catastrophic vibrations.
Currently, particular signal control devices known as proportional valves are used to apply variations in braking power to railway cars. In many instances, the proportional valve is connected directly to the railway car and has mechanical components for measuring the weight of the car. Based on the measurement of the weight, the proportional valve works to apply the appropriate amount of braking power to the railway car.